Particle separation and sorting represents an important requirement especially in biological and chemical processes for both macro-scale and miniaturized lab-on-chip applications. Macro-scale methods include: mechanical sieving, sedimentation, and free flow fractionation (FFF). Micro-scale methods include: hydrodynamic chromatography, size exclusion chromatography, electrophoresis, miniaturized FFF, ultracentrifugation, and ultrafiltration. These methods are extremely laborious and require skilled technicians even for routine operation.
In commonly assigned U.S. application Ser. No. 11/224,347, filed on Sep. 12, 2005 (now U.S. Pat. No. 7,681,738 issued Mar. 23, 2010) and entitled “Traveling Wave Arrays, Separations Methods, and Purification Cells”, which is hereby incorporated herein by this reference, a device such as that shown in FIG. 1 is described. Such a device serves as a single-step concentration/focusing/separation device for particles that are suspended in fluid which may be configured for both batch and continuous flow operation. The combination of traveling wave grid layouts and sample separation strategies may be incorporated together with the concentration and focusing aspects of the device to provide a purification cell 600 as shown in FIG. 1. The purification cell 600 includes a concentration chamber 610, a focusing channel 650, and a separation chamber 670, 680. The top 680 of the separation chamber may be divided into a lateral row of compartments 682, 684, 686, 688, and 690 to collect an increasing range of particle sizes proceeding from left to right. For example, relatively large sized particles constitute the stream denoted by arrow 672, which are subsequently collected in compartment 690. Intermediate sized particles constitute the stream denoted by arrow 674, which are subsequently collected in compartment 688. And relatively small sized particles in stream 676 are collected in compartment 686. Streams of finer sized particles can be collected in one or both of the compartments 682 and 684. The traveling wave arrays in the separation chamber may be a continuous layout of chevrons to focus particulates in the different size ranges into the designated collection compartments at the top. The focusing section 650 forms a narrow stream which will result in improved separation performance. Representative dimensions for each portion or component of the cell 600 are provided on FIG. 1.
FIG. 2 shows another exemplary embodiment traveling wave array 700 where a connecting bridge is utilized and disposed between the top to close the loop on the cell. This strategy allows the contents of one of the collected compartments to be re-circulated to result in increased purification. The purification cell 700 includes a concentration chamber 710, a focusing channel 750, a separation chamber 770, 780, and a connecting bridge 740. The top of the separation chamber may be divided into a collection of compartments 782, 784, 786, 788, and 790 to collect an increasing range of particle sizes proceeding from left to right. For example, relatively large size particles constitute the stream denoted by arrow 772, which are subsequently collected in compartment 790. Intermediate sized particles constitute the stream denoted by arrow 774, which are subsequently collected in compartment 788. And relatively smaller sized particles in stream 776 are collected in compartment 786. Streams of finer sized particles can be collected in one or both of compartments 784 and 782. The connecting bridge 740 can be utilized to selectively return particles of a particular size or size range, to the concentration chamber 710 if further processing is desired.
This device is modular and is potentially suited for disposable use. However, the trapping functionality of the device could be improved to make trapping of appropriately sized particles more convenient and reliable. Also, improved trapping systems could be useful in a variety of implementations apart from the devices of FIGS. 1 and 2.